A tractor for over-the-road hauling is purchased for $90,000. It is expected to be of use to the company for 6 years, GO after which it will be salvaged for $4,000. Calculate the depreciation deduction and the unrecovered investment during each year of the tractor's life. a. Use straight-line depreciation b.Use declining-balance depreciation, with a rate that ensures the book value equals the salvage value C.Use double declining balance depreciation d. Use double declining balance, switching to straight-line depreciation e.Use sum-of-years -digits depreciation